We know that dogs have a highly developed sense of smell that allows them to flush out their prey when hunting, locate people buried under the snow, and find drugs or even explosives. But are dogs also capable of detecting disease, especially cancer? Certainly, some studies claim that this is possible, but under what conditions? What is it really? Find out the answers to your questions and much more in this complete file.
Can dogs smell cancer in humans?
The dog's sense of smell: a highly developed sense
Dogs have a highly developed sense of smell, which is estimated to be between 10,000 and 20,000 times more powerful than that us humans. They prove it every day thanks to their ability to detect drugs, explosives, an imminent earthquake, a nearby store, a gas leak, a missing person, etc.
In the field of health, it is proven that dogs are a precious help. Indeed, it has been proven that the presence of dogs helps the elderly and the sick to feel better; their general state of health naturally improves in contact with these animals.
So can we imagine that dogs would be able to really detect cancer? And if so, in what context? Are all dogs able to do this? Are all forms of cancer detectable? At what stage of the disease does the animal feel it? There are many questions!
Dogs and cancer detection
It was in the late 1980s that the idea that dogs could detect cancer first appeared. Indeed, several testimonies of affected people revealed that their dog sniffed their cancerous mole, their breast, their belly, etc. In 1989, dermatology professor Hywel Williams reported the case of a melanoma patient. Unaware that she had cancer, she was concerned about the strange shape of a mole on her leg until her dog kept sniffing it and barking. This is how the disease was diagnosed in this patient. In the face of the multitude of other reports, scientists became interested in the question of whether dogs are indeed capable of detecting cancer in humans or whether it was a "fluke".
Studies have been carried out in many laboratories located in several countries around the world. In France and Germany, researchers have demonstrated the ability of certain dogs to detect prostate cancer in urine, intestinal cancer in stool, and lung cancer in the breath of affected patients.
At the Institut Curie, an experiment was conducted with explosive detection dogs. After specific training, the dogs were able to recognize all the women with breast cancer among wipes soaked in sweat. It turns out that these women had only recently been diagnosed and had not yet undergone any treatment. This suggests that the dogs smelled the cancer molecule and not the scent of any drug.
The tests also found that the dogs were able to detect the disease in patients in remission. In fact, the animals reacted in the case of a woman in remission from breast cancer, but a recurrence was detected 18 months later by MRI. So the dogs had sensed it well in advance!
Can dogs distinguish between different forms of cancer?
Scientists set out to understand the ability of dogs to detect cancer and wondered about the olfactory compound released by cancer cells. Indeed, the objective was to know if dogs can detect all cancers or only some and if the different forms of the disease emit the same odor or if each cancer has its own olfactory imprint.
Studies have been conducted on dogs trained to detect breast cancer. However, it turned out that the animals were able to detect several other forms of cancer cells in a wide range of diseased and healthy human tissue samples. It seems that dogs sniff out the same molecule for all forms of cancer. This is a real asset because it makes training easier! All that remains is for medicine to do its work!
What are the real capacities of the dog in terms of cancer detection?
The various experiments carried out have shown that dogs can detect cancer in affected patients. They perceive the chemical compounds emitted by the tumors and present in the body of the affected persons. They can detect their presence in the breath, skin, urine, stool, as well as in tissues taken from the patients.
However, it should not be assumed that all dogs have this ability. All dogs indeed have a highly developed sense of smell, which is more or less refined and powerful depending on the breed. It is quite possible that a small doggie can detect cancer in its owner, as shown by this patient and her cancerous mole. However, the reliability of such a claim can only be based on animals that are trained to smell this specific scent. Breeds with a better sense of smell are the Basset Hound, German Shepherd, Pointer, Brittany Spaniel, Beagle, and Labrador.
And what about the future?
The challenge now lies in the ability to identify the precise olfactory compounds emitted by cancer to make them early markers and act well before the disease. Prevention is the key because too many cancers are detected too late after several months or years of discreet development without symptoms, which often does not allow patients to be saved in time or forces them to undergo very heavy treatments that do not protect them from the risks of recurrence.
Some cancers, such as ovarian cancer, have a high mortality rate because of their complex diagnosis. Conversely, other cancers such as prostate cancer are sometimes poorly identified. Indeed, the PSA test is the only current test and its lack of reliability gives many false positives, which often leads to unnecessary treatments and operations.
It seems that dogs can detect cancer well before it is detectable by thorough medical examinations. In terms of prevention, this "sixth sense" is a blessing. Unfortunately, this practice cannot be generalized nowadays and the presence of dogs in medical environments in general - and hospitals in particular - is still inconceivable today. However, it is known that dogs are also capable of detecting other diseases, such as diabetes, high blood pressure, epileptic seizures, autism, or Asperger syndrome. Their usefulness for our health is no longer to be proven. Nevertheless, research continues, which is at least a good thing.